1. Field of the Invention
The present application is an application claiming a priority on the basis of a Japanese Patent Application No. 2005-308163 filed to Japan on Oct. 24, 2005, and the content in this Japanese Patent Application is incorporated by reference herein, so as to constitute a part of the specification of the present application.
The present invention relates to an optical information recording medium, and a method for manufacturing an optical information recording medium. The invention relates in particular to, for example, an optical information recording medium wherein a recording/reproducing-side main surface thereof is covered with a protecting layer having a low frictional coefficient, and a method for manufacturing the optical information recording medium.
2. Description of the Related Art
In recent years, in the field of information recording, various research on optical information recording has been advanced. This optical information recording makes it possible to attain high-density record and perform non-contact record/reproduction. Thus, the application of the recording to a wide scope is being realized as a manner capable of realizing the record/reproduction at low costs. Examples of existing optical discs include compact discs (CDs) having a capacity of about 700 MB, which has a structure wherein an information layer is deposited on a transparent resin substrate of 1.2 mm thickness and the resultant is protected with an overcoat, and digital versatile discs (DVDs) having a capacity of about 4.7 and a structure wherein one or more information layers is/are deposited on one or two surfaces of each of two transparent resin substrates each having a thickness of 0.6 mm and the two are caused to adhere onto each other.
In recent years, as a method for raising the recording density of optical discs, the following methods have been investigated: a method of making the numerical aperture (NA) of an objective lens large; and a method of making the wavelength of a laser to be used as short as 400 nm. Optical discs called Blu-ray Discs or HD DVDs have been suggested.
In such optical discs, a protecting layer which is not easily damaged has come to be deposited over the recording/reproducing side surface thereof in accordance with a request that the reliability of recorded information should be certainly kept, a request that a handle-ability such that the discs can each be used without being put into a cartridge, and other requests. As the recording density of optical discs becomes higher, required performances of the protecting layer also become higher. Thus, a coating agent which has a larger hardness and a smaller frictional coefficient is being developed, as described in Japanese Patent Laid-open Publications No. 2002-190136 and No. 2002-230837.